The present invention pertains to a foreign object (e.g., stone, piece of metal, etc.) detection method and apparatus for detecting and removing discrete hard non-frangible objects from mobile agricultural equipment. Specifically, self-propelled combine harvesters and forage harvesters are adapted with an apparatus that performs the method of detection of rocks and other discrete hard objects to permit the reliable removal of rocks and non-frangible objects from harvested crop material during crop harvesting operations.
In the context of this disclosure, unless indicated otherwise, the phrase “non-frangible objects” will be used generally to refer to any hard non-frangible objects of at least a minimum size that may be picked up by a harvesting machine in a field including but not limited to stones, rocks, pieces of metal, pieces of wood, etc. In at least some embodiments the minimum size will be approximately three inches in length or diameter although the present invention should not be so limited. In other embodiments the minimum size may be anywhere from one inch to five or more inches in length or diameter.
In the art of mechanically harvesting crops, it is known that self-propelled agricultural vehicles, such as combine harvesters and forage harvesters, are used to mechanically harvest crops. Typically, these vehicles are equipped with a harvesting implement, or header, that includes a reel for pulling crops into an array of blades for cutting the crop, wherein the cut crop material is pulled further into the header along a transport surface by an auger. Once past the auger, the cut crop material is carried by an elevator to a threshing and sorting mechanism that removes unwanted chaff material from the desired crop matter before the crop matter reaches a storage compartment carried by the vehicle.
The above described simple crop harvesting process is complicated by the fact that non-frangible objects are often pulled into the header with the crops. Unfortunately, non-frangible objects (e.g., stones, pieces of metal, etc.) can cause damage to the elevator and threshing mechanisms. To minimize equipment damage from non-frangible objects, various methods and apparatuses have been developed to detect and remove non-frangible objects from the header before the cut crop material is carried by the elevator into the threshing and sorting mechanism.
An exemplary stone ejecting system may include an active system which utilized some sort of an electronic sensor, such as an acoustical transducer typically in the form of a piezoelectric disc mounted in a sensing plate in conjunction with a stone trap. The electronic sensor responds to the characteristics of the sound, such as the amplitude and frequency, that an impacting stone generated in the sensing plate. This signal would then be transferred through an electronic circuit that filtered out the range within which the amplitude and frequency was characteristic of stones. Within this characteristic spectral range the electronic circuit automatically activated a latch releasing mechanism on a door along the bottom of the in-feed housing that would pivot open to permit the stones or hard objects to be ejected from the feeder house, along with a small amount of crop material.
An exemplary detection/ejection system includes a sensor, a sensing plate including a sensing surface, a discriminating circuit and a solenoid operated trap door. Here, the sensing plate and trap door are consecutively placed along the path of harvested material travel. The sensor is often a piezoelectric ceramic disc linked to the sensing plate and generates signals indicative of the type of material that impacts or is currently on the sensing plate. For instance, the sensor may generate signals whenever a stone or the like impacts the sensing surface of the plate or when a stone vibrates on the sensing plate. Here, signal characteristics known to be associated with non-frangible objects are known (e.g., amplitude and frequency of vibrations, signatures associated with impacting stones, pieces of metal, etc.) and the discriminating circuit is designed to distinguish characteristics of non-frangible objects from characteristics associated with harvested crop materials. When a non-frangible object is detected, a signal is provided to the solenoid causing the solenoid to open the trap door so that the non-frangible object is ejected from the system.
Unfortunately, several factors make it difficult to accurately distinguish non-frangible objects from harvested crop materials. First, as harvested material is transported over the sensing surface, non-frangible objects are usually mixed in with harvested crop material so that the non-frangible objects often do not make direct contact with the sensing surface. In these cases the harvested crop material operates as a type of muffler to stifle the signals associated with the non-frangible objects thereby making it difficult to distinguish those objects from the harvested crop materials.
Second, despite efforts to isolate the sensing plate and sensor from other harvester components, in many applications harvester and harvesting related noise (e.g., harvester engine vibrations, jarring of the vehicle as it travels along the ground, rocks impacting the exterior of the header during harvesting operations, etc.) make it difficult to distinguish non-frangible objects from harvested crop materials. Consequently, unless signal characteristics indicative of non-frangible objects are precisely known and the discriminating circuit is precisely tuned to pick up the non-frangible object signal characteristics, incorrect object identifications can occur which lead to either opening of the trap door when not necessary and loss of crop material or passing of non-frangible objects to the elevator and threshing mechanisms resulting in damaged equipment.
Thus, it would be advantageous to have a mechanism or apparatus that could increase the accuracy of non-frangible object detection in harvesting machines.